Stephen Daisley left the national broadcaster in January after earlier complaints from SNP politicians about his commentaries.
Mr Daisley claims that nationalist MPs John Nicolson and Pete Wishart pressured STV bosses in an effort to stop him writing.
Revealing his new role as a Daily Mail columnist on his blog, he gave his account of why he abruptly stopped publishing articles in August last year:
“Wishart began hectoring STV about me on social media and I was immediately concerned,” Mr Daisley said.
“When a colleague found himself uninvited to press conferences at one Glasgow football club, STV stood by him — for a day, before capitulating and sending another journalist to cover the story.
“I didn’t fancy my chances.
He continued: “Soon Nicolson, who sits on the powerful Westminster media committee, joined in. I was summoned to a meeting with STV’s head of digital and head of news and told my role was being changed.
“I could edit STV’s politics page or I could write but I could no longer do both.
“I couldn’t believe this was happening.
“Two SNP MPs had used the bully pulpit of Twitter to lean on STV and STV had caved.”
Mr Daisley also attacked the SNP’s ten years in power and believed they had “divided the country”.
“Across ten years, the SNP has concentrated power, stifled dissent, bullied opponents, and divided the country along a nasty dichotomy of nationalist vs unionist,” he said.
“Much of the blame lies with Alex Salmond, Scotland’s first First Minister of any stature but also our first post-liberal leader.
“For all their protestations about “civic” nationalism, the SNP under Salmond was instrumental in the cowing of non-nationalist Scotland.”
The SNP have resolutely denied their Westminster members attempted to gag Mr Daisley.
A party spokesman previously said: “At no point have the SNP or any of its parliamentarians asked for Mr Daisley to stop writing, and any suggestion otherwise is completely untrue.
“Any editorial decisions are entirely – and rightly – a matter for STV.”
STV also denied the claims.